Creature Feature by Dr Gerald Goeden

Gerry Goeden is a Malaysian based marine ecologist. He works with reef fish, artificial reefs, shark conservation, and dolphins in the Andaman Sea. Visit his underwater world through interesting stories about the marine life he encounters.

Saturday, 9 August 2014

If you are ready for a weird creature meet the Japanese Spider Crab. This
scary arthropod (the world’s biggest) has a leg span of almost 4 metres and can
weigh over 20 kg. Lucky for us it eats dead fish and smaller crabs 300-800
metres below the surface.

The Japanese spider crab has 10 legs. The front two legs are
longer and have evolved into enormous claws (chelipeds) with a 3 m reach. The
rounded shell that forms its body may be 30 cm in width and up to
40 cm long. The compound eyes are made up of clusters of hundreds of
simple eyes. The eyes are protected by two strong thorns that stick out between
them.

They are only found on the Pacific side of Japan
and are fished around Suruga Bay. They are
considered a delicacy and overfishing is rapidly reducing their numbers.

They grow slowly and reach an age of perhaps 100 years. Luckily, there are
new measures to protect this weird crab. The Japanese Spider Crab is Macrocheira
kaempferi.

Saturday, 28 June 2014

Man’s best friend may be the dog but
today, a sailor’s best friend is a marine mammal. I know; this is a very controversial subject but let's just look at some facts.

Sea lions and dolphins served in the
military during the first Iraqi war. The animals were used to detect mine
fields that were placed to blow up American ships. Contrary to some reports,
the marine mammals are treated very well. They are given the best food and
their trainers are with them night and day. They are too expensive and too important to be treated badly.

Because these animals work in open
water without the supervision of the trainer the marine mammal will only return
to the ship if it wants to. Training is based on a bond of trust between the marine mammal and the trainer. The work has to be fun and mentally
stimulating as well or the marine mammals lose interest. remember, they are intelligent animals and get bored with routine.

This dolphin is carrying a camera on
its flipper and signaling that it has finished its photo mission. The sea lion
is fitting a recovery line to lost equipment.

The Navy doesn’t take any chances
with injuring their ‘divers’ because training is too expensive and replacements
can take years to train.

Sea lions have the advantage over
dolphins in being able to climb into boats and helicopters; dolphins have to be
transported in large tanks of water or follow their trainer’s speed boats.

Civilians have
been working with sea lions for search and rescue in open water. Some research
facilities now take their dolphins into the ocean for exercise. They return to
their pens when they have had enough and want to spend time with their
trainers.

Dr. Ted
explained, “This kind of work with marine mammals requires a lot of careful
interaction with the animals. They have to trust us as much or more than they
trust a member of their own species. Working as partners with marine mammals is
probably the best part of my job.”

Friday, 9 May 2014

Box jellyfish have
cube shaped bodies and are considered to be more complex than other jellyfish.
Because they have such powerful stings box jellyfish are called sea wasps. The
best-known species of box jellyfish is Chironex fleckeri. It is part of
a dangerous group of about 19 different species.

Box jellies live in Australia,
the Philippines, Hawaii, Vietnam,
and many other tropical seas. Box jellyfish are extremely venomous and have
killed many people. The Chironex fleckeri and the Carukia barnesi
(called Irukandji) have the most powerful venom of any animal in the world.

Stings from such species are extremely painful and are often fatal. Box
jellyfish stings are believed to have caused more than 5,500 deaths (Wikipedia).
A severe sting can kill in as little as 3-4 minutes. Sometimes a person who
gets stung will have a heart attack or drown before they can return to the
shore or boat.

The tiny Irukandji is thumb-nail size.

Scientists have calculated that the amount of venom in one animal is enough
to kill 60 adult humans. Most of the box jellyfish sting comes from tiny cells
on its trailing tentacles. There are about 500,000 stinging cells (called
nematocysts) on each tentacle. Each stinging cell is equipped with a
microscopic harpoon that shoots out and injects a tiny amount of venom. The
venom has several effects attacking the victim’s nervous system, heart, and
skin.

The stinging cells are activated by touching another living animal. When scuba
diving with box jellyfish, Reef Ninja Scientists wear special thin ‘lycra’ dive
suits that don’t trigger the stings. Wearing gloves and a hood protects the
rest of our bodies.

The biggest box jellyfish is Chironex
fleckeri. It grows to the size of a small melon and it is this species that
has caused most of the deaths. Surprisingly, the thumbnail-sized Irukandji is the next most dangerous being
responsible for serious stings requiring hospitalization and even several
deaths. Many cases of drowning are thought to be caused by the intense pain of Irukandji
stings.

Friday, 18 April 2014

There are approximate 25 species of Dolphins
and each species has its own distinct personality and behaviors. Some of the
species are easily kept in huge aquaria and it is there that we can learn much
about these amazing animals. The
Bottle Nose Dolphin is the most studied of all Dolphin species. We have about 6 species here in the Andaman Sea that show up regularly.

Bottle Nose Dolphins in an aquarium.

When
traveling in the open ocean, Dolphins can cruise at 30 kilometres per hour.
Scientists thought there must be something special about their skin. Now we
know that Dolphin swimming muscles are very powerful and the high speed comes
from lots of hard work. Dolphins also leap out of the water when swimming fast;
they do this to increase their average speed and save energy.

Dolphins use a range of
clicks, whistles, and squeaks to communicate with each other and to locate both
prey and predator. Sending out sounds and waiting for their return creates a
picture in the Dolphin’s mind similar to our sight. The process is called
echolocation.

This Dolphin is using echolocation to find fish buried in the sand.

Clicks to home-in on a fish
meal may be produced at 1,000 every second. When the prey is close some
Dolphins use a very loud ‘pop’ to stun it and make the catching easier. With
all that swimming a Dolphin eats about 10-15 kg of food each day.

A 'bait ball' of small fish is attacked by a pod of Dolphins. Schooling protects the fish but the Dolphins keen sonar will pick out an individual and follow it to capture.

Dolphins travel in groups
called pods. Males spend a lot of time fighting with each other to determine
who will be boss and get the best females for mates.

All of the males keep watch
over the females so they can’t swim away to another pod. If they try to escape,
they are bitten or hit by the males’

bodies. Of the 25 species,
the Bottle Nose Dolphin is the most aggressive and will fight every day.

Dolphins do things we can’t
understand. These Dolphins have learned to slide up onto the bank to eat the
mud. Are they searching for minerals in their diet or does it just taste good? Because they learn by copying, they all use their right side and they have
all worn down their right teeth. This has gone on for generations.

Being a Dolphin can be
dangerous! Killer Whales and Tiger Sharks both prey on Dolphins. Seventy percent of wild Bottle Nose Dolphins
carry some form of scars from fighting or escaping from predators.

A Killer Whale attacks a Dolphin and its calf with such force that they are thrown out of the water.

There is continuing debate over the ethics of keeping Dolphins in captivity.

On the one side, it's safe to say that there would probably be little protection of wild Dolphins today if some weren't kept where people could see them. Understanding brings protection in our world.

On the other hand, Dolphins are thinking, self aware, social animals that normally travel great distances every day. Is it fair to keep them in an artificial environment?

Wednesday, 9 April 2014

Megalodon is a Greek name given to a now extinct giant shark that roamed
the world’s oceans between about 2 and 25 million years ago. Megalodon
literally means “big tooth”. It is the fossilized teeth that tell us much about
what we now know was a ‘super predator’; the king of the oceans.

The teeth were so large that early finds were once
believed to be petrified tongues of the dragons.

Estimates vary, but we are
confident that Megalodon grew to about 15 metres in length and quite
possibly to 30 metres and was the largest shark ever to exist.

Megalodon (gray and red) with the whale shark (violet), great white shark (green), and a human (black) for scale. Note: The maximum size attained by megalodon is indicated by the 20 m scale. Wikipedia

Scientists
are certain that Megalodon preyed on whales, dolphins, and possibly giant sea
turtles. Whale bones (including vertebrae and
flippers) have been found with clear signs of large bite marks made by teeth
that match those of Megalodon. Additionally, some geological excavations have
found the giant teeth with the chewed remains of ancient whales.

In 2008 Dr. Stephen Wroe conducted experiments to
determine the bite force of Megalodon. He found that very large specimens were
capable of exerting a bite force of up to 275 Mpa (40,000 pounds per square
inch); over 5 times greater than that of T.
rex).

Megalodon was probably the most powerful predator to have lived on
Earth.

Most sharks are opportunistic; they will feed on a wide
range of species and even scavenge for food. Some large sharks (including the
great white shark which is a distant relative of Megalodon) attack their prey
with great force.

Their strategy is to inflict as much damage as possible and
then follow their prey until it dies from blood loss. This not only saves
energy but avoids the risk of injury in a fight to the death.

Scientists believe that Megalodon was no different than
today’s big sharks. Fossil evidence shows that Megalodon attacked the larger
whale’s flippers (with their large blood vessels) and the rib cage. In both
instances the prey would have bled to death quickly.

Sharks like Megalodon have ‘sawing’ teeth that can carve
out huge chunks of meat from their victims.

A reconstructed jaw of Megalodon shows the replacement teeth that would move up to maintain a sharp bite.

Megalodon’s jaws would have opened
to a size of 2m wide and 2.3 m high. Its bite could have held as much as 5-6 m3
of flesh or about 6 tonnes of food.

Sunday, 9 February 2014

My interest in sharks was
like everyone’s – morbid. A shark attack with photos was front page news and
each sparked debate in the dive clubs over the best way to avoid becoming the
next victim. I sometimes carried a ‘bang stick’ so I could fight these villains
if it came to the worst.

When I started work on the
Great Barrier Reef , I got a surprise. The sharks seemed bigger, more numerous,
and very brave compared to their Caribbean brothers. Australian shark attacks
were front page stories and dominated the news for days.

And yet there I was working
for hours every day, year after year within metres of these predators and all I
had to do to avoid trouble with the tropical species was respect their
territories and not swim around with speared fish on my belt.

So how real is the case against sharks?

Every year about 100
shark attacks are reported worldwide. In 2011,
just 17 fatalities were recorded as having being caused by sharks, out
of 118 attacks. Although shark attacks
are infrequent, there is a heightened awareness due to occasional serial
attacks; “it’s out there and it’s after me”. Horror fiction like Jaws appears on TV just often enough to
keep this fear alive and even “nature” shows only show sharks in frenzied
feeding.

Shark attack experts are adamant that the danger has been greatly
exaggerated.
According to theInternational Shark Attack File(ISAF), between the years 1580 and 2011 there were 2,463
confirmed unprovoked shark attacks around the world, of which 471 were fatal. Surprisingly,
that’s only 1.09 fatalities per year for the last 431 years.

Australiais ranked
second in terms of global shark attacks with 877 attacks since colonial
settlement in the 18th century; it’s ranked the highest in terms of
shark fatalities, with only 217 during this long period.

The results of
Gore’s Michigan State University study reviewing worldwide media coverage of
sharks found that more than 52 percent of global coverage focused on attacks on
people and sharks were portrayed as aggressive and dangerous in nearly 60
percent of the reports. Positive PR was tougher to find with only 10 percent of
stories dealing with shark conservation and just 7 percent looking at biology
and ecology.

According to Time/ CNN
: Zoologists today estimate elephants around the world kill 500 people a year
while the great white sharks (Jaws) kill only 4 people.

Incredibly,
there are about 24,000 lightning deaths (one every 20 minutes) and 240,000
injuries worldwide annually (Royal
Aeronautical Society, 2003). When was the last time we read stories of
the lurking danger above or watched a movie where people were struck down like
dominoes by searing thunder bolts?

Why is shark conservation so important and why is it being
neglected?

The first part of this question is
easy. Sharks are in big trouble. "Overfishing of sharks is now recognized
as a major global conservation concern, with increasing numbers of shark
species added to the International Union for the Conservation of Nature's list
of threatened species," say Mizue Hisano, Professor Sean Connolly and Dr
William Robbins from the ARC Centre of Excellence for Coral Reef Studies and
James Cook University.

Why we are
neglecting shark conservation is harder to answer. First, there have been
powerful economic reasons to turn a blind eye to shark fishing and shark finning.
These may not have been good reasons but greed is a characteristic of human
behaviour and we make lots of poor decisions because of it.

A second
explanation comes from deep in the primitive part of our brains. Our
prehistoric ancestors had the very same fears that we do according to Psychology Today. We were ‘designed’ to
be afraid; fear was our operating manual for things we didn’t understand or
that could do us harm. Fears protected our ancestors.
“Our distant ancestors who were afraid of heights didn’t fall off cliffs, those
that feared wild animals didn’t get eaten, those that ran the fastest left the
rest behind---and they survived.”

Elephants are
not on our list of feared animals and we donate millions of dollars each year
to protect them even though they kill thirty times more people than sharks. Why
can’t we see that the health of our ocean hangs in the balance and that we are
making decisions with our ancestor’s fears and not with our future in mind?